Police are secretly photographing up to 14million motorists a day and keeping their details for years, it has emerged. Images of drivers and their front seat passengers are being captured by a network of cameras and held on a database without their knowledge, a police document has revealed.

Now police chiefs are facing a legal challenge from privacy campaigners, who say that automatic number plate recognition cameras are being used to spy on innocent road users.

Police and the Highways Agency have previously claimed that ANPR cameras on the roads do not transmit images of drivers.

But internal guidelines produced by the National Policing Improvement Agency show that in some areas ANPR ‘routinely captures the faces of front-seat occupants’.